The present invention relates to an image forming apparatus and an image forming method, and more particularly, to an image forming apparatus and an image forming method for producing a booklet composed of different size pages.
Japanese Patent Publication (TOKKAI) No. 2000-72320 has discloses a sheet post-processing device (finisher). The sheet post-processing device performs a saddle stitching operation on a plurality of sheets having an image recorded thereon and discharged from an image forming apparatus, and folds the sheets along a stitched portion thereof to bind a booklet. The sheet post-processing device performs the saddle stitching operation and the folding operation with edges of the sheets aligned. The finished booklet becomes neat with the edges of the sheets aligned and with all pages having the same size.
As more and more handicapped and aged people participate in social and corporate activities, a variety of efforts are made to provide an environment friendly to these people in corporate offices and government offices, for example.
A booklet bound by a conventional sheet post-processing device has typically aligned edges. The booklet with the page edges neatly aligned looks good, but it is difficult for people who are forced to use a single hand to open pages, for example.
Japanese Patent Publication (TOKKAI) No. 8-164686 has disclosed a sheet post-processing device for producing a booklet providing an easy page turning feature. The booklet is produced by performing a saddle stitching process or a folding process on a sheet stack with edges of the sheets successively shifted from one page to a next page.
The booklet having the easy page turning feature with the edges of the pages shifted presents the following problem. In such a booklet, an area of each page is different from page to page (see FIG. 20).
When an image having a size for a booklet having the same sheet size is formed on the pages having different areas, the image may be formed out of a page having a small area. As shown in FIG. 21(B), when images are formed next to each other on the same surface of a sheet at a position away from an edge opposite to a stitch line (fold line) by a predetermined distance m, the image is positioned out of the page one having the smallest area. As shown in FIG. 21(C), when the images are formed next to each other on the same surface of a sheet at a position away from a stitch line (fold line) by a predetermined distance m, the image is positioned out of the page one having the smallest area and a part of the image is cut.
In the booklet having the easy to turn page feature, the edges of the pages are shifted. Therefore, it is easy and reliable to turn the pages with fingers holding the shifted portion. Since there is a predetermined shift between, for example, page one and page three, it is easy to find a borderline between the two pages and a position on which the user can place a finger to turn a page.
However, in the case that the images are formed on the shifted portion of each page, it is difficult to find the borderline between the pages and the position on which the user can place a finger to turn a page. Further, in an aesthetic point of view, a booklet with images formed on the shifted portion does not look good.
The images may be formed on each page with an extra space from the edge of the page having a width equal to or larger than a shift to prevent the image formed out of the shifted portion in the booklet. In that case, however, when the images are formed on an odd-number page and an even-number page, corresponding to the front and back of one sheet, at positions away from the edge of each page by a distance equal to or longer than the shift, the user can not find the image on the even-number page, i.e. the back of the one sheet, without opening pages wider than in a booklet having all pages aligned, thereby causing an inconvenience to the reader.
Accordingly, it is an object of the present invention to provide an image forming apparatus and an image forming method for forming images on each page of a booklet having different size pages without cutting the images on any page.
It is another object of the present invention to provide an image forming apparatus and an image forming method for making a booklet in which it is easy to turn the different size pages.
In view of above mentioned problems, it is yet another object of the present invention to provide an image forming apparatus and an image forming method for producing a booklet having different size pages with edges of the pages shifted by a predetermined distance to allow a reader to quickly recognize the images formed on each page.
Further objects and advantages of the invention will be apparent from the following description of the invention.